1. Field of the Invention
The invention relates to thermal responsive devices, and in particular, to thermal responsive devices employing gas adsorbent materials.
2. Description of the Prior Art
The prior art, as exemplified by U.S. Pat. Nos. 2,221,633, 2,426,663, 2,627,911, 2,787,130, and 3,410,141, contains many thermal responsive devices which have enclosed chambers containing an activated material, such as activated charcoal, with a gas charge, such as difluorodichloromethane, dimethyl ether, carbon dioxide, argon, nitrogen, trifluoromonochloromethane, or fluoromethane. Activated charcoal is made by eroding funnel-like pores or cavities in carbonized organic materials such as wood, coal, coconut husks, bones, etc. by a reactive material, such as steam, carbon dioxide or the like. While gases in activated-charcoal-containing devices exhibit some increase in volume or pressure change per degree of temperature change over devices containing only gas, attempts to manufacture such activated charcoal devices in quantities have generally met with failure; it has been impossible to predict or avoid large variations in volume or pressure change per degree temperature change in different batches of activated charcoal; the increase in volume or pressure change per degree temperature change was not sufficiently large to warrant the added manufacturing cost; and the activated charcoal devices were substantially deficient in volume or temperature change per degree temperature change compared to alternate devices, such as liquid-vapor or mercury expansion devices.
The prior art, as exemplified in U.S. Pat. Nos. 1,744,735, 3,258,363; 3,442,819; 3,516,791 and publication (USSR Academy of Sciences, M. M. Dubinin, "Thermal Treatment and Microporous Structure of Carbonaceous Adsorbents" Proceedings of the Fifth Conference on Carbon, Volume 1, 1962, pages 81-87), contains many adsorbent carbon materials including decomposed polyvinylidene chloride and polyvinylidene fluoride. Adsorbent carbon materials are widely used in removing contaminants, or the like, from gases or liquids. POlyvinylidene chloride and polyvinylidene fluoride, in particular, have been recognized for their "molecular sieve" property, that is, their ability to adsorb certain gaseous materials which have small molecular sizes while being incapable of adsorbing other gaseous materials which have larger molecular sizes.